The use of 2,2,6,6-tetraalkyl-4-piperidylamines, such as N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine, as ultraviolet stabilizers for polymeric materials is well known in the art. In the past, the production of these compounds has generally involved the use of a platinum catalyst in an aliphatic alcohol solvent.
Thus, U.S. Pat. No. 4,104,248 issued to G. Cantatore shows the production of various N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)amines employing a platinum on carbon catalyst and utilizing methanol as a reaction medium. Similarly, U.S. Pat. No. 4,326,063 issued to P. N. Son discloses a process for producing 2,2,6,6-tetraalkyl-4-piperidylaminocycloalkyl compounds utilizing a platinum catalyst and a polar organic solvent, such as an aliphatic (lower alkyl) alcohol, while Minagawa et al in U.S. Pat. No. 4,415,688 show the production of certain 2,2,6,6-tetraalkylpiperidylamine compounds employing a platinum/carbon catalyst and methanol as the solvent. In the same vein, U.S. Pat. No. 4,293,466 to Di Battista et al shows the production of N,N'-4-piperidyl-tetraalkyl-substituted alkylene compounds in the presence of a hydrogenation catalyst such as platinum.
However, as is shown in Table I below, the yield of product when a platinum catalyst is employed in a low pressure (100-200 psig) process is relatively low. While the use of higher pressures (e.g., of 600-800 psig) will increase product yield somewhat, as is indicated in Table II below, such high pressure platinum-catalyzed processes will also result in the production of a relatively substantial amount of unrecyclable byproducts (such as 2,2,6,6-tetramethyl-4-piperidinol and the like).
An alternative approach is disclosed in German Offenlegungschrift No. 3,007,996, wherein a Raney nickel or cobalt catalyst is employed in an inert organic solvent to produce polyalkylpiperidylamines. The stated benefit of this process is that low hydrogen pressures of between 5 and 30 bar (between about 72.5 and 435 psi) may be employed. It is noteworthy that the Examples of this publication indicate that at pressures of 20 bar (about 290 psi) the yields of product ranged from 82-93 percent.
From the above, it is apparent that it would be desirable to possess a process for the production of 2,2,6,6-tetraalkyl-4-piperidylamines in increased yields. Moreover, it would be desirable to possess a process for preparing such piperidylamines which would result in reduced amounts of unrecyclable byproducts, such as piperidinols, being produced.
Accordingly, it is an obJect of this invention to provide a process for the production of 2,2,6,6-tetraalkyl-4-piperidylamines which process would provide increased yields.
It is a further object of this invention to provide a process for the production of 2,2,6,6-tetraalkyl-4-piperidylamines which process results in the production of reduced amounts of unrecyclable byproducts.
The above and additional objects will become more apparent from the following description and Examples.